Climate change and the thermal physiology of aquatic insects: emerging patterns and unresolved questions

Aquatic insects are among the taxa most vulnerable to climate change, yet their capacity to cope with rising temperatures remains poorly understood. Here, we review current knowledge of the thermal physiology of aquatic insects, with a focus on metabolic rate and thermal tolerance. Thermal responses are commonly summarized using thermal performance curves, and we examine key properties of these curves including thermal sensitivity, upper and lower thermal limits, and plasticity. Species inhabiting thermally variable environments often exhibit reduced metabolic rates and lower thermal sensitivity, while temperate species generally display broader thermal breadths and greater acclimation capacity than tropical species. However, support for these patterns is inconsistent across taxa. For example, mayflies and stoneflies from similar habitats frequently show divergent thermal responses, suggesting that plasticity is shaped not only by environmental variability but also by taxon-specific physiological traits. Oxygen availability plays a central role in mediating responses to warming. Hypoxia can amplify acclimation responses in thermal tolerance, and respiratory mode strongly influences both heat tolerance and its plasticity. Cross-study comparisons will require careful consideration of methodological differences, including exposure duration and experimental design. We conclude that aquatic insect responses to climate change emerge from interactions among temperature, oxygen availability, exposure duration, and taxon-specific physiology. Resolving these interactions will require integrative experiments spanning a broader diversity of aquatic insects.